Before the onset of presbyopia, the natural optical lens in the human eye has the ability to alter its focal length (e.g., to vary depth of field and focal plane) so as to focus objects at varying distances from the observer onto the observer's retina for visual interpretation by the observer's brain. With increasing age and the resulting onset of presbyopia, the eye lens progressively loses its ability to change focus and view with clarity objects that are outside a limited range of focus distances. This inability of the eye lens to change its focal length with age results in poor visual quality outside of a fixed focus distance. Additionally, lower and higher order aberrations (a common side effect of various types of refractive surgery) in the eye can lead to reduced visual quality, particularly in low illumination, which can present as symptoms of glare, halos, or reduced contrast sensitivity.
Current treatment methods for ameliorating the adverse effects of these losses in visual quality include short-term pharmacological treatment (e.g., the use of miotic agents) for losses in low light vision due to higher order aberrations as well as vision corrective surgeries that attempt to alter the focal distances of the human eye lens in order to improve the range of clear vision. The use of medical miotic agents is generally used only as a short-term solution due to decreasing efficacy and the potential for adverse side effects. Vision corrective surgeries have generally been found to be inadequate in reversing the effects of presbyopia that occur with age.